The structure of the mature eutherian sperm chromosome will be investigated by physical, chemical, enzymological and microscopic techniques. Specifically, the molecular mechanisms involved in sperm chromatin condensation and decondensation will be investigated. Also, the detailed subunit structure of fully decondensed sperm chromatin will be examined using electron microscopy, micrococcal nuclease digestion, chemical structural probes and sperm protein cross-linking reagents. The results of these structural studies of decondensed sperm chromatin will be compared to recent structural studies of somatic chromatin in order to determine similarities and differences between the chromosomal material of mature sperm cells and somatic cells.